Overwatch developer Blizzard confirmed Mei's changes and bugs. On Blizzard's PTR Feedback forum, players were asking questions about the changes made to Mei in the recent experimental update. A Blizzard employee, Josh Nash, responded to these concerns.
Overwatch Mei Changes and Bugs: Blizzard Employee Responds
Mei Cannot be Healed by Teammates While in Cryo-Freeze
This has been confirmed as an unmentioned nerf and was intentional. Mei can no longer be targeted by teammates while in Cryo-Freeze. This is a relatively minor nerf, but it is strange that changes to Mei weren't mentioned in the PTR patch notes.
Mei's Freeze Rate is Slightly Slower
Players tested and discovered that Mei's freeze rate went from 30 to 31 clicks in the PTR. Nash says this is an unintentional bug and that the team at Blizzard will look into it.
Mei's Cryo-Freeze Does Not Stop Enemy Abilities
Nash has confirmed that this is a bug because Reinhardt's change should end when it hits Mei in Cryo-Freeze. Currently, Reinhardt's charge and other similar abilities pass through Mei's ice block without harming her. While this bug will likely not cause drastic problems it is strange to see.